why does the sky turn red at sunset?

Answer 1

As the sun crosses the horizon, the atmosphere acts as a prism, refracting the different colors of light.As the violet-indigo-blue sequence goes by, it is lost in the general blue of the sky. The yellow-orange-red sequence is lost in the reddish color of the sunset.Between these two sequences is green, which stands out vividly against the blue of the sky, and the red of the sunset.

Answer 2

I read this in a book once, it was something to do with the angle of the sun to the earth. Basically the sun gives out white light which has a whole spectrum of colours in it (as demonstrated by rainbows or prisms). When the sun is low in the sky at sunrise or sunset, we can see the redder end of the spectrum.

I'm not sure why we never see the blue/indigo end although that would be interesting!

The book I saw this in was a collection of questions answered in New Scientist magazine.

Answer 3

The light you see when you look at the sky is sunlight that is scattered by particles of dust in the atmosphere. If there were no scattering, and all of the light travelled straight from the sun to the earth, the sky would look dark as it does at night. The sunlight is scattered by the dust particles in the same way as the light from the flashlight is scattered by particles in milk in this experiment. Looking at the sky is like looking at the flashlight beam from the side: you're looking at scattered light that is blue. When you look at the setting sun, it's like looking directly into the beam from the flashlight: you're seeing the light that isn't scattered, namely orange and red.

What causes the sun to appear deep orange or even red at sunset or sunrise? At sunset or sunrise, the sunlight we observe has traveled a longer path through the atmosphere than the sunlight we see at noon. Therefore, there is more scattering, and nearly all of the light direct from the sun is red.

Answer 4

In the day time the sky is blue due to the reflection of the oceans by the atmosphere acting like a mirror, which is why you can't see stars in the daytime. (You can see the moon cos its brighter than stars). When the sun sets, drops lower on the horizon, it is not high enough to reflect off the oceans, so we get direct sunlight (orange/firey colour) reflecting directly off the atmosphere. Hence orange sky. At night there is no light to reflect (unless in a large city) so you can see through the atmosphere and see the stars. The atmosphere (sky) is sort of like a window. Cool hey??

Answer 5

Light from the sun consists of a range of wavelength covering all the spectrum ie visible sprectrum - blue to red. As the sun sinks (or rather as the earth rotates on is axis) the light form the sun needs to pass through a greater amount of our atmosphere.

To make an analogy consider you have a friend in scuba gear at the bottom of a swimming pool that rotates, while you stay in the same position....a midday you are standing on the edge of the pool above him and you dive in ...you only need ot swim a small distance to reach him. However 6 hours later the pool has rotated and now you are standing at the other end of the pool ...to swim to him you need to swim through a lot more water.

The same with sunlight, but light is absorbed by the atmosphere by different amounts depending on its wavelength. Blue light is absorbed first and so on until you only see red light. Thus, as the sun sinks it goes from white to yellow to orange to red (as each wavelength is gradually absorbed). This light is then reflected from underneath any clouds in your line of sight, creating the sunset you see.

Answer 6

It isn't red... it's considered a yellow star. It isn't setting the earth is revolving away, and the sun isn't really there although we see it. It is actually an optical illusion since light takes a few minutes to reach the earth after leaving the sun. Now we see it as red because only its low end spectrum colors reach our vantage point. The rest of the visible spectrum; yellow, green, blue and purple can be seen reflecting off cloud tops at higher angles.

Answer 7

Dust and pollution in the air reflect the pretty colors of sunset.

Answer 8

Sun light travels greater distance through atmosphere than it would if its shining directly above your head (since sun is low on horizon). As light (mixture of different colors) travels through the atmosphere other colors (shorter light waves, blue) scatter away and you receive what's left (longer light waves, red).

Answer 9

Combine the answers of Clair, Ace, and Deep, and you've got a pretty good explanation, without getting into complex physics and astronomy.

Answer 10

its the angle under which the light enters the atmosphere.... this determines how the light breaks and thus what colours are visible, same reason why a cloudless sky is blue...